Shoot RAW and you’ll have less noise. OK, you and I both know that among RAW’s many benefits over JPEG, lower noise isn’t one of them. Or is it? Well, yes and no.
Technically, the level of noise you see in a JPEG can (should) be exactly the same as RAW, depending on the RAW conversion, not on JPEG’s inherent noise. But look at the following pictures, noticing specifically the decreasing noise levels between them: (These are screen shots pulled out of Aperture, thus the red highlighting in a few places.)
(Technical note: All three shots are identical in camera except for exposure. All three RAW files were adjusted identically except for exposure and recovery. D300 @ ISO 400. 1/2500@f/5.6, 1/1250@f/5.6, 1/640@f/5.6)
Due to the Heron’s bright white feathers, the first shot is the greatest exposure I could get by with without blowing them out. It’s actually a 2 stop underexposure compared to what the meter suggested. Then in Aperture I gave it one stop boost and brought back the highlights with recovery. In effect, this is the best I could have done with a JPEG. (In fact the shadows are better due to the greater dynamic range maintained in the RAW file. JPEG would not have had the same amount of data available.) Note the very noticeable noise in the background. Also, note in the pupils (and in many of the other background areas not visible in the crop) you can see a lot of dark areas that are pure black.
The second shot was given an additional stop in the camera. This is the correct exposure for most of the scene, with the white feathers being the major exception. So, in Aperture I left the exposure flat and just dialed in the same amount of recovery as the first one to regain detail in the white feathers. That couldn’t have been done with a JPEG, as there would have been no data available to help out the feathers. Note the much lower noise levels. Also, all of the dark areas have detail in them.
Finally, the third shot was exposed as the camera meter suggested, giving a one stop overexposure to the scene. In Aperture I pulled back the exposure by one full stop and matched the same recovery setting of the other two pictures. As expected this gives a near exact exposure match for the other two. The 14-bit RAW file from the D300 sensor has plenty of headroom to handle the highlights which are blown out by 1.75 stops, so I am able to bring them back to be basically the same as in the other two exposures. The real benefit here, though, is the further reduction in noise. It looks pretty good!
So does RAW have less noise than JPEG? No. But it does give you the headroom to overexpose by one, one and a half, maybe even 2 stops and then pull the exposure back in post, effectively reducing the noise levels and increasing the amount and quality of the detail in your shadow areas.
Had I thought of it at the time I would have also shot this at ISO 200 to determine if the overexposed shot (final shot above) had lower noise than I would have gotten simply by reducing the ISO. The difference seems more dramatic than the nearly invisible difference between ISO 200 and 400, so I think this is better, but I’ll have to try it out to be sure.